The prior art includes various double-walled plastic vessels, both resealable and non-resealable. Resealable examples include thermoses and like containers. Non-resealable examples include various double-walled tea and coffee cups (i.e., tumblers) and related items.
The prior art also includes transparent liquid holding vessels. These include a wide range of containers often formed of any of the standard commercial plastics. Examples include clear plastic soda and fruit juice bottles, soup and other liquid containers, and water bottles. Polyethylene terephthalate is an example of a plastic used to fabricate single use water bottles.
Higher end water bottles and like devices are known that are made of a polycarbonate resin sheet material. Polycarbonate is favored in some applications because it exhibits resistance to odors and flavors and thus different tasting beverages can be placed in a container with less likelihood of a taste “memory” from the previous beverage. Polycarbonate resin sheet material is also relatively durable compared to many conventional beverage container plastics. One commercial source of polycarbonate is General Electric which sells this material under the trade name “Lexan.” Nalgene is one maker of water bottles and laboratory equipment that are made of single walled polycarbonate.
Notwithstanding the benefits of polycarbonate, it is disadvantageous, among other reasons, in that it is relatively difficult to work with. It tends to be more viscous and rigid than other plastics and joining two components made of polycarbonate typically requires a weld that is unsightly.
Furthermore, relative to other types of beverage container plastic, the polycarbonate raw material is expensive. Coupling the material cost with the elevated cost of manufacture (associated with the difficulty in working with polycarbonate) renders polycarbonate products disadvantageously expensive.
Accordingly, due to problems associated with cost of material, difficulty in manufacturing, joining components and/or hiding unsightly joints, etc., prior art vessels using polycarbonate have been limited to single wall vessels or double walled vessels with only a single wall of polycarbonate material. The benefits of having a double walled polycarbonate vessel, for example, durability, insulating, transparent, non-odor absorbing, potentially microwave-able, etc., are not realized.
A need thus exists for a double walled polycarbonate liquid holding vessel that overcomes the deficiencies of the prior art and achieves some or all of the above stated benefits. A need further exists for a double walled polycarbonate liquid holding vessel that is resealable and at least in part transparent.